Rounding Calculator

How to use it

1. Type the number you want to round.
2. Choose whether to round to decimal places, a nearest value, or significant figures.
3. Pick standard rounding, round up or round down, and read the result.

What is rounding?

Rounding replaces a number with a shorter, approximate one that is easier to read and compare. The standard rule looks at the first digit you are dropping:

if the next digit is 5 or more, round up; otherwise round down

So 3.14159 rounded to two decimal places becomes 3.14, because the dropped 1 is below 5, while 2.678 becomes 2.68. Rounding to a nearest value snaps a number to the closest multiple, turning 1,247 into 1,250 at the nearest ten. Significant figures keep a fixed count of meaningful digits instead, starting from the first non-zero digit, which is the convention in science and engineering.

Worked example

One number, every rounding setting

Rounding rules that trip people up

Standard rounding sends a 5 or higher up and anything below 5 down, so 3.145 rounds to 3.15 at two decimals and 3.144 rounds to 3.14. Rounding 3.14159 to two places gives 3.14, and to four places gives 3.1416. Rounding to a nearest value, like the nearest 25 or 1,000, snaps the number to the closest multiple: 1,247 becomes 1,250 to the nearest 10, 1,200 to the nearest 100 and 1,000 to the nearest 1,000. That is how prices, budgets and estimates are usually reported.

Significant figures count from the first non-zero digit, so 0.004821 to three significant figures is 0.00482, and 123,456 to three is 123,000. Rounding up (ceiling) and rounding down (floor) ignore the halfway rule and always move in one direction: 4.01 rounded up to a whole number is 5, and 4.99 rounded down is 4. That matters for container counts, pricing tiers and safety margins, where you cannot ship 4.2 boxes or state a load limit rounded in the generous direction.

Halves, negatives and floating point

This tool uses the half-up rule taught in school: 2.5 becomes 3, and for positive numbers that matches Excel's ROUND function. Some software uses banker's rounding instead, where an exact half goes to the nearest even digit, so 2.5 becomes 2 and 3.5 becomes 4; Python's built-in round() works that way. Negative numbers have a quirk here: an exact half rounds toward the higher value, so −2.5 becomes −2 while −2.51 becomes −3.

Computers store decimals in binary, and a value like 1.005 is actually held as a hair less than 1.005. Rounded to two places it can come out as 1.00 rather than the 1.01 you might expect. For money, the safe habit is to round once at the end of a calculation rather than at every step, and to double-check any input that ends in exactly 5.

Common uses

• Trimming decimals to a clean number
• Rounding prices to the nearest dollar or 25 cents
• Reporting figures to significant figures
• Estimating with round hundreds or thousands
• Rounding up to whole boxes, tiles or seats
• Checking homework on rounding rules

When to use it

• You need to round to two decimal places for a money amount on an invoice.
• Homework asks you to round to the nearest hundred and you want to check your answer.
• A chemistry lab report calls for three significant figures.
• You are buying tile or paint and must round up to whole boxes, never down.
• You want budget numbers in clean thousands for a quick presentation.
• You are checking whether software that rounds 2.5 down used banker's rounding instead of the school rule.

Related tools

The Sum Calculator produces the exact total you may want to round afterward.

The Average Calculator gives means and medians with long decimals worth trimming here.

The Percentage Calculator handles tips and discounts before you round to whole cents.